Resistor type isolator for lightning arresters



April 10, 1951 o. H. KAMINKY .2,548,112

REsIsToR TYPE lsoLAToR FoR LIGHTNING ARREsTERs Filed Aug. 6, 1949 IN VEN TOR.

Z ornez/ Patented Apr. 10, 1951 RESISTOR TYPE ISOLATOR FORLIGHTNINGARRESTERS Oscar H. Kaminky, South; Milwaukee, Wis., assignor to McGrawAElectric Company,V a corporation of Delaware Application August 6,1949,"Serial'N0. 108,878

(Cl. G-115) 5 Claims.

Thisinvention relates to a resistor type of isolator for lightningarresters.

Heretofore it has been the practice to provide an isolator for lightningarresters which is associated with a lightning arrester having sparkCircuit-Interrupting Device owned by the as- 5 signee of the presentinvention.

Prior forms of isolators have been found to have radio interferencewhich resulted from a charge accumulating on the upper electrode of theisolator and discharging to the lower electrode, thereby producing acorona effect, with resulting radio disturbance.

This invention is designed to overcome the above noted defects andobjects of this invention are to provide a novel type of isolator whichis so made that a resistor provides a path for the discharge from theupper electrode to the lower electrode of any slowly accumulatingcharge, the resistor being of high enough value so as to prevent thefree connection of the electrodes of the isolator and also being of highenough value so as to insure the sparking over from the upper electrodeto the cartridge having the explosive charge within the resistor or elsethe heating of the cartridge due to the heating of the resistor so as tocause the charge to explode and rupture the isolator, therebydisconnecting the lightning arrester from the ground.

"Further objects are to provide a very simple construction of resistortype isolator which is compact, which may be readily made, and which maybe easily assembled with the usual type of lightning arrester withoutany alterations of the lightning arrester itself.

An embodiment of the invention is shown in the accompanying drawings, inwhich- Figure l is a side elevation with parts broken away showing thelightning arrester with the isolator in place.

Figure 2 is an enlarged view partly in section through the isolatorshowing it removed from the lightning arrester.

Referring to the drawings, it will be seen that the lightning arresterhas been indicated generally by the reference character I and consistsof a series of conducting members 2 forminga series of gaps 3 arrangedfor connection between the power line 4 and valve material 5, whichlatter has negative resistance characteristics. The lightning arrestermay have a ceramic body part of cylindrical shapeyand anupper cap orcover l of linsulating material. It is provided with a lower terminal 3into which is screwed theconnecting threaded portion 9 of an `,upperterminal of an isolating device indicated generally by the referencecharacter l0. This isolating device has a second terminal or lowerterminal II which is connected by means of a flexible ground conductorI2 to the groundas'indicated in Figure 1.

The isolating device is shown more in detail in Figure 2 and it will beseen that the upper ter minal consists of 'the disk-like member I3 whichhas the threaded stem 9 previously described, It also has a lowerterminal consisting of a'disl:` like member I4 having the lower threadedpor tion II.

The upper and lower terminals or rst and'V second terminals I3 and I4 ofthe isolating device are in abutting relation to the upper and lowerfaces of'an annular insulating spacing member or breakable shell I5.This shell is weakened by means of an annularY groove 'I6' intermediateits ends. Preferably, fastening means I6 in the form'of screws extendthrough the disks I3 and I4 and into the breakable shell I5. Thebreakable shell-surrounds an annular resistor il which is composed ofnegative resistance material such as siliconcarbide commonly known asGranulon. lThis-resistor may be of a compacted form so as to retainitsannular shape as shown in Figure 2,-or may be a Ypowder held in placeby suitable means not shown.

The lower terminal I4 is provided with a hollow upwardly projecting stemI8 which carries an explosive charge such as the loaded cartridge i9.Preferably the upper terminal I is provided with a centrally locatedsparking tip 2t.

-The isolator operates in substantially the same manner as that of theisolator of the patent hereinabove mentioned. However, this isolator hasan additional and different function from that of the prior isolator. Asstated hereinabove, it has been found that there is an accumulation ofcharge on the upper electrode so that there is a diierence in voltagebetween the upper and lower electrodes. This causes a corona effect orslight sparking or slight discharge which produces radio interference.The provision of the resistor I1 of negative resistance material servesto effectively conduct away any accumu- 3f lated charge and to thusprevent radio interference. Itis preferable that the negative resistancematerial have relatively high resistance so that the upper and lowerterminals of the isolator are substantially electrically separate. Thereis, however, a sun'icient amount of conduction to prevent the radiointerference hereinabove noted.

When an excessive amount of current flows, the explosive charge isignited either by sparking or by the heating of the resistor I1, theresult being the same in both cases. The charge explodes, thus breakingthe shell or casing I5 and allowing the bottom terminal of the isolatorto drop away and electrically disconnect thelightning arrester from theground.

It will be seen that a very simple type` isolator has been providedwhich is of the resistor type and adds to the heretofore knownadvantages of the isolator, such as shown in the prior patent, theadditional features enumerated above thus eliminating radiointerference.

Although this invention has been described in rconsiderable detail, itis to be understood that .such description is intended as illustrativerather than limiting, as'the invention may be variously embodied and isto be interpreted as claimed.

I claim:

1. The combination of a lightning arrester having one end arranged forconnection to a power line and having a second end, an isolating devicehaving a rst terminal connected to the .said second end of saidlightning arrester and having a second terminal connected to the ground:and having an annular breakable shell normally holding said first andsecond terminals apart, an :explosive charge arranged to explode andbreak :said shell on excessive flow of current from said rst to saidsecond terminals, and a resistor composed of negative resistancematerial bridging the said rst and second terminals of said isolatiingdevice.

2. The combination of a lightning arrester having one end arranged forconnection to a power line and having -a second end, an isolating devicehaving Va first terminal connected to the said .second end of saidlightning arrester and having a second terminal connected to the groundand ,Thaving an annular breakable shell normally holding said rst andsecond terminals apart, an explosive charge arranged to explode andbreak :said shell on excessive flow of current from said irst to saidsecond terminals, and a resistor composed of negative resistancematerial bridging the said rst and second terminals of said isolatingdevice, said resistor being annular and surrounding said explosivecharge.

3. The combination of a lightning arrester having one end arranged forconnection to a power line and having a second end, an isolating devicehaving a rst terminal connected to the said second end of said lightningarrester and having a second terminal connected to the ground and havingan annular breakable shell normally holding said first and secondterminals apart, an explosive charge arranged to explode and break saidshell on excessive flow of current from said first to said secondterminals, and a resistor composed of negative resistance materialbridging the said iirst and second terminals of said isolating device,the explosive charge being in close proximity to said rst electrode andto said resistor and arranged to be ignited on excessive ow of currenteither by sparking between the lrst and second electrodes of saidisolating device or by the heating of said resistor.

4. ,The combination of a lightning arrester having oneend arranged forconnection to a power line and having a second end, an isolating devicehaving a i'lrst terminal connected to the said second end of saidlightning arrester and having a second terminal connected to the groundand having an annular breakable shell normally holding said rst andsecond terminals apart, an explosive charge arranged to explode andbreak said shell 'on excessive flow of current from said rst to saidsecond terminals, an annular resistor surrounding said explosive chargeand bridging the terminals of said isolating device, said i-lrst andsecond terminals abutting the ends of said shell, and fastening meansextending through said first and second terminals and i'nto said shell.

5. The combination of a lightning arrester having one end arranged forconnection to a power line and having a second end, an isolating devicehaving a first terminal connected to the said second end of saidlightning arrester and having a second terminal connected to the groundand having an annular breakable shell normally holding said first andsecond terminals apart, an explosive charge arranged to explode andbreak said shell on excessive flow of current from said first to saidsecond terminals, an annular resistor surrounding said explosive chargeand bridging the terminals of said isolating device, said first andsecond terminals abutting the ends of said shell, and fastening meansextending through said first and second terminals and into said shell,said shell having an annular weakened portion intermediate its ends.

OSCAR. I-I. KAMINKY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,967,616 Hillebrand July 24,1934 2,118,795 Littleton May 24, 1938 2,174,477 Pittman et al Sept. 26,1939 2,283,685 McCreery et al. May 19, 1942 2,305,436 McMorris Dec. 15,1942 2,315,320 Earle Mar. 30, 1943

